As is well known and understood, there exists a need for a handheld message entry terminal for use by a forward military observer to enter short messages into a computer based system for analysis. For example, a forward observer may be called upon to transmit, in digital format, various informations concerning the terrain in an area under his surveillance so that troop movements may be planned aforehand. In typical applications, the forward observer may be called upon to transmit information describing natural terrain--the location of a cave, a lake, a river, or a ridge, etc.--, man-made terrain--the location of a cemetery, a road, a railroad crossing, for example --, the existence of fortifications--e.g., an airfield, a permanent building, a gun emplacement, a landing strip, a trench--, or the existence of obstacles to troop movement--amongst which might be the presence of barbed wire, minefield, a crater, or a roadblock.
Such message terminals as have existed heretofore for use by a forward observer have not provided optimum performance capabilities. The well known "walkie-talkie", for example, requires conversion of the audio information into digital form for use by the computer based system, and suffers the further disadvantage that its use is not limited to the rigid message information format readily accepted as one of the most efficient means of communications in a coded communications network. Attempts at utilizing digital signals for coded transmission in accordance with formats set down in code books suffer the disadvantage that the books can be lost or can be damaged by inclement weather, and suffer the added disadvantage that the code books can be used at night only after first being illuminated, thereby providing a means of announcement of one's presence in an area and damaging security. Whereas the conversion to light emitting diode or plasma panel displays have obviated the problems attendant with these code books, there is associated with them both a complexity of design and an associated high cost. Additionally, the large amount of power needed to operate these devices during daylight conditions has resulted in these message systems being both bulky and unmanageably heavy for effective forward operator use, weighing in the order of 10-12 pounds, and more.